Straddle carriers

ABSTRACT

The straddle carrier has two spaced parallel elongated frame members adapted to straddle a load. A pair of vertically disposed arch member connects the frame members together adjacent the ends thereof and diagonally disposed brace members connect the tops of the arches to substantially the mid-points of the frame members. Ground wheels are flexibly mounted on the undersides of the frame members, and means for steering the wheels are provided. A rectangular load lifting beam is disposed between the frame members and arches. Means are provided engaging the four corners of the lifting beam for raising and lowering the lifting beam, means being provided at the four corners of the lifting beam for securing same to a load. Means are also provided for guiding the lifting beam during its ascent and descent. And means are provided for controlling the lifting beam raising and lowering means whereby the four corners of the beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on the respective corners, in order to maintain the beam always parallel with the frame members.

[151 3,655,081 [451 Apr. 11,1972

United States Patent Monk ABSTRACT [54] STRADDLE CARRIERS Primary Examiner-Albert J. Makay Attorney-Alexander and Dowell PAENTEnAPRmsIz 3,655,081

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PATENTEDAPR 1 l |912 SHEE 110F12 PATENTEDAPR 1 1 |912 SHEET 1a nr 12 NN GQ STRADDLE CARRIERS DESCRIPTION OF INVENTION This invention relates to straddle carrier type material-handling vehicles so designed that the load to be carried is suspended within the framework of the vehicle, the vehicle may be of such size and proportions as to permit engaging, hoisting, stacking and transporting van-sized containers.

Prior art machines of this type are subject to very high accident rates caused by poor visibility. They have mechanical failures caused by weak frame structures and complicated lift systems.

The principal objects of my invention are to provide a straddle carrier which has excellent visibility and a strong, simple, smooth structure. These objectives are attained in numerous ways, some of which are as follows:

The main frame of my invention consists of spaced parallel elongated frame members which are connected together adjacent their ends by means of vertically disposed structural arches to form a rigid rectangular frame. One of said arches carries adjacent its upper end the cab for the driver in which is disposed the steering wheel and various controls for the vehicles. The arches are braced by diagonal bracing connecting the arches adjacent their upper ends to substantially the midpoints of the frame members, respectively.

Supporting wheels are flexibly applied to the underside of the frame members, three wheels being provided on each side below each frame member, the center wheels of which are fixed, while the outer wheels are simultaneously actuated regardless of the radius of curvature of any steering course in such manner that the projection of the axles of the outer wheels, both those of the inner frame and outer frame members, will always intersect the projection of the axles of the center wheels at a common point for all radii of curvatures in steering.

Within the vehicle is a container lifting beam comprising an outer member and an inner member, the latter being shiftable laterally and longitudinally with respect to the outer members. The ends of the inner member of the lifting beam extend beyond the ends of the outer member and carry at the corners thereof rollers adapted to engage telescoping guides disposed on or adjacent the legs of the arches to guide the lifting beam during its vertical ascent and descent. Adjacent the guides are4 upwardly disposed fluid cylinders carrying upwardly extensible rams, said cylinders being connected with their respective frame members by universal joints to permit universal movements of the upper ends of the cylinders while preventing rotational movement thereof. The comers of the outer member of the lifting beam are connected to one end of cables extending from said corners up and over pulleys on the upper ends of the respective rams, the other end of the cables being connected to the frame members adjacent the said universal joints, whereby as the rams of the hydraulic cylinders are extended upwardly by hydraulic pressure the four corners of the lifting beam will be simultaneously raised or lowered to thereby raise or lower a van-sized container or the like which is attached at its four corners to the underside of the lifting beam at the four comers thereof by conventional coupling members. Means are provided for simultaneously actuating the cylinders to raise or lower the lifting beam and the van-sized container attached thereto within the frame of the vehicle, said means including a fluid circuit so arranged that the said comers of the lifting beam are simultaneously raised or lowered equal amounts notwithstanding the relative weights on said respective corners, so as to maintain the van-sized container at all times parallel with the machine frame.

Heretofore, straddle carriers have been provided in which the frame is of general horizontal U-shape, i.e., in a horizontal plane, the frame being open at one end only, lthe same having a connecting arch at one end only, but it has been found that the stresses imposed are on such long moments that it is very difficult to prevent frame breakage in the center section of the arch; and in order to help this situation the lift cylinders on such prior art machines have been rigidly mounted on the frame and were connected at their upper ends with a cross member; but it has been found that this imposes severe bending loads on the lift cylinders, and results in broken cylinders and severe wear on the piston and sealing leathers.

Another object of my invention is to provide rigid rectangular frame having connecting arches near each end, so that the vehicle can straddle a load of equal height from each end, the outer rounded ends of the frame members acting as guides for the container as it passes between the frame members. ln my design the lift cylinders being connected with the frame members by universal joints, leaves the lift cylinders free of all outside bending stresses and they support only the load.

Heretofore, such prior art machines have been provided in which the lift cylinders have been connected together with a cross member from which the lifting beam is suspended; but in my design the lifting beam is suspended directly from the lift cylinders. This removes another obstruction to vision.

Heretofore, in such prior art machines the vertical guide tracks for the lifting beam having been attached directly to the cross members which connect the lift cylinders and the guide tracks move up or down with the cross membenFurther the tracks are restrained by guide bars in the side frame members and are only free to move vertically.

Another object of my invention, however, is to provide a construction in which the vertical guide tracks are stationary until such time as the lifting beam rises to the tops of the arches, after which the guide tracks are raised by the guide rollers on the ends of the lifting beam engaging plates at the tops of the tracks when the beam is lowered, the tracks descend until they reach the starting point, at which place they stop, but the lifting beam is free to continue its downward movement without further movement of the guide tracks.

Heretofore in such prior art machines, the lifting beam itself is usually suspended some distance from the point where it attaches to the load. Hence a cantilever or bending load is imposed on the lifting beam. However, a further object of my invention is to provide an arrangement in which the lifting cables for the lifting beam attach directly over the point where the load itself is lifted; therefore my lifting beam supports nothing, but merely acts as a spacer to keep the lifting hooks or twist locks in proper relation to one another.

Heretofore in such prior art machines the lifting beam must have a fixed length because of the rigid cylinder design. However, my design enables the use of telescoping beam or lift frame because the lift cylinders are free to swing on their frame members, and because the rams in my design can rotate on their columns of fluid to align with the attaching points on the beam. This is important because of variations in the lengths of containers.

Heretofore in such prior art machines the engine, transmission and all drive components are disposed on the platform above the front arch with the operator; but it has been found that such machines are top heavy and unstable. Moreover, visibility is very poor and a crane or elevated platform is needed to do many minor repairs.

A further object of my invention is to provide a design which removes all power components from high elevations and places them low in the structure where they contribute to stability, and are low enough to be reached from a ladder, or may be removed by use of a small fork-lift, common everywhere. In my design there are no members connecting the lift cylinders to interfere with the operators vision, and no power train components surround the operator. Furthermore, there are no horizontally extending frame members in the upper side frames to further restrict vision. The arch at the opposite end of the frame is far enough from the operator so as to obstruct a relatively small area.

ln such prior art machines a long chain drive is used for each drive wheel, reaching from the power platform to the drive wheel, which chain limits the amount the drive wheels can cut," or steer, and for that reason they must resort to uneven spacing of the support wheels, involving severe steering angles on those furthest from the drive wheels. It has been found that in order to secure an acceptable turning radius, the machine must have a short wheelbase. This results in instability in a fore-and-aft direction. The projecting chain and guard are frequently damaged in collision accidents.

A still further object of my invention therefore is to provide a design which uses hydraulic or hydrostatic power which is transmitted to the drive wheels through flexible hose. For that reason the steering angles can be whatever the designer fancies up to and including a 90 cut This makes it possible to space the wheels evenly on the machine, which in turn makes it unnecessary to steer the center wheels hence simpler steering. Since the steering angles can be greater it is no longer necessary to keep the wheelbase short and therefore it may be made longer with improvement in fore-and-aft stability. As in my design there are no chains and guards to knock off, another set of problems are eliminated.

Other minor objects will be hereinafter set forth.

I will explain the invention with reference to the accompanying drawings, which illustrate several practical embodiments thereof, to enable others familiar with the art to adopt and use the same; and will summarize in the claims the novel features of construction, and novel combinations of parts, for which protection is desired.

In said drawings:

FIG. 1 is a perspective view of my novel straddle carrier showing the lifting beam in lowered position.

FIG. 2 is a view similar to FIG. 1 but showing a lifting beam in elevated position.

FIG. 3 is a side elevation of the carrier as shown in FIG. 1.

FIG. 4 is a side elevation of the carrier as shown in FIG. 2.

FIG. 5 is an end elevation of the carrier as shown in FIGS. 1 and 3.

FIG. 6 is an end elevation of the carrier as shown in FIGS. 2 and 4.

FIG. 7 is a top plan view of the carrier.

FIG. 8 is an enlarged end view of the lifting beam showing the rollers at the ends thereof engaged in the vertical guides.

FIG. 9 is an end elevation showing the lifting beam and the adjacent portions of the ram, and showing the rollers of the beam engaging the vertical guides.

one another adjacent each end thereof by inverted U-shaped arches A and B formed of structural plates and angle bars, both arches A and B being of substantially the same construction and serving to keep the main frame members 60-60a in proper spaced relation with one another, and to provide clearance for the frame to straddle a load to be handled from either end thereof. Said arches A and B comprise pairs of vertical legs 61 having their lower ends resting upon and secured to the respective main frame members 60-60a, the upper ends of the vertical legs of each pair being connected together by horizontal beams 61a of structural plates and angle bars. The

arches A and B are in turn stiffened by diagonal braces 62 FIG. l0 is a side elevation showing the lifting beam and lift- A ing ram in lowered position on the vehicle frame member. This also shows that the lift cylinder is not vertical. It always leans inward to some extent. The angle will vary slightly as the lifting beam is displaced.

FIGS. 11 and 12 are plan views illustrating the arrangement of the actuating mechanism for the steering wheels of the carrier.

FIG. 13 is a side elevational view of the said steering mechanism shown in FIGS. 1l and 12.

FIG. 14 is an elevational view of the hydraulicsystem for simultaneously raising and lowering the four corners of the lifting beam, showing the beam in raised position.

FIG. 14a is a view similar to FIG. 14, but showing the beam in lowered position.

FIGS. 15 and 16 show details.

FIG. 17 illustrates a modification of the means for shifting the load-carrying beam transversely of the carrier frame.

FIG. 18 is a sectional view showing one unit of suspension of the wheels in intermediate position.

FIG. 19 is a sectional view showing one unit of suspension fully compressed.

FIG. 20 is a sectional view showing one unit of suspension fully extended.

FIG. 21 is a side elevation of the vehicle frame showing one method of operatively connecting two units of suspension.

THE MAIN FRAME The main frame of the vehicle comprises two spaced parallel elongated horizontal frame members 60 and 60a formed of structural plates and angle bars or square tubing connected to disposed over the main frames 60-60a extending from the upper ends of the vertical legs 61 respectively to approximately the mid-points of the main frames 60-60a, the purpose of said diagonal braces 62 being to relieve the vertical members 61 of the arches of torsion loads and bending loads caused by fast braking and acceleration of the vehicle.

The main frames 6,0 and 60a are supported respectively by three equally spaced wheels 63, 63a, 63h under frame 60, and wheels 64, 64a, 64b under frame 60a, which are mounted on trunnions extending into the frames 60-60a. The trunnions of all the wheels are free to move vertically against flexible supports and the trunnions of wheels 63, 63b, 64, 64b are rotatable about their vertical axes. However, the trunnions for the center wheels 63a and 64a are attached to main frame members 60-60a respectively by linkage 65 (FIGS. 3 and 4) and are thus prevented from rotating about their vertical axes. Thus, the wheels 63a and 64a always remain parallel with the axis of the main frame members 60-60a of the vehicle.

The wheels 63, 63h, 64, 64b at the ends of the frames 6(L60a however are steerable and are connected through tensile members and bellcranks in such a manner as to cause the vehicle to steer around the projection of the shafts of the center wheels 63a, 64a. In tum the fore-and-aft wheels 63, 63h, 64, 64b on any given side of the frame will rotate through the same but opposite angularity due to the use of bellcrank quadrants 66, 66a and 70, 70a coupled by drag links 7l, 71a (FIGS. 11, 12 and 13) which are proportioned so as to cause the axle projections of such wheels to pass through a common point on the projection of the axles of the center wheels 63a, 64a, wherever such wheels are turned from a straight-line position.

The force required to steer the vehicle is supplied by an engine driven pump 72 (FIGS. 3 and 4) supplying hydraulic pressure to double acting cylinders 73 and 73a (FIGS. 1l, 12 and 13) attached respectively to the main frames 60 and 60a and to their respective bellcrank quadrants 66 and 66a. The hydraulic pressure and flow is controlled by a valve disposed adjacent the steering wheel 74 in cab 75. In this manner full hydraulic power operated steering is accomplished.

The operator is housed in a cab 75 mounted on the front face of the cross beam 61a of arch A in such a manner as to give the best visibility possible. All controls for driving or hoisting are also located in cab 75. The engine 66 for hoisting and propulsion is mounted on top of the main frame member 60 nearest the operators cab 75. The engine 66 has a gear case 67 (FIGS. 3 and 4) mounted on its power end which drives several hydraulic pumps and other accessories. One of the pumps is of the variable displacement type and is connected to drive the motors 68 (FIGS. 1 and 2) on the hubs of wheels 63 and 64 respectively. The pumps on the engine and the wheel motors are connected through suitable pipes and flexible hose connections allowing unlimited steering angles.

THE STEERING MECHANISM The wheels 63, 63d, 63b, 64, 64a and 64b are flexibly attached to the main frames 60-60a. The wheels on each frame 60-60a are equally spaced along the frame so that the distance from wheel 63 to 63a is the same as from wheel 63a to 63b. The distance from wheel 64 to 64a is the same as from 64a to 64b. The center wheels 63a-64a on each side frame 60, 60a

are each non-rotatably fixed to the frames with a linkage 65, which permits vertical movement but does not pennit the trunnions of said wheels 63a, 64a to rotate in their respective frames. Thus, the wheels 63a and 64a are not steerable. The trunnions for the remaining wheels 63, 63b, 64, 64b each has a pulley or sprocket 100 (FIG. 11-12) attached to it. Tensile members 67-67a which may be cables, chains, or a combination of solid and flexible cables, are threaded around the pulleys 100 of wheels 63, 64, as shown in FIGS. 11-12, serving to rotate their related trunnions about their vertical axes and thus to achieve steering.

As shown in FIG. l2, tensile member 67 is attached to quadrant 66, journaled on the underside of frame 60, and threaded around the pulley 100 for trunnion of wheel 63. The ends of tensile member 67 are supported on quadrant 66 by compressible members (Lord mounts, or springs) in order to compensate for the radius effect on member 67. Tensile member 67 is also secured to the pulley 100 for trunnion of wheel 63 so that no slippage will occur and said trunnion will rotate in the same direction as quadrant 66.

A tensile member 68 is attached to quadrant 66 and is threaded around and secured to the pulley 100 on the trunnion of wheel 63b, but tensile member 68 has its runs crossed over as shown in FIG. 12, in order to cause the trunnion of wheel 63b to rotate in a direction opposite from quadrant 66 and also from the trunnion of wheel 63. The ends of tensile member 68 are supported on quadrant 66 by compressible members (Lord mounts, springs, etc.) in order to compensate for radius effect on tensile member 68.

Since the trunnion sprockets or pulleys 100 are all the same size and are equally spaced, it can be seen that a projection of the axles of the respective wheels 63 and 63b will coincide at some point along the projection of the axle of wheel 63a if such wheels are turned to any position which is not parallel with the main frames. The point at which this will occur moves nearer to or further from frames 60 or 60a depending upon the steering angularity of wheels 63 and 63b.

Similarly, as shown in FIG. 11, a tensile member 67a in (FIG. 11) is attached to quadrant 66a, journaled below main frame 60a and is threaded around pulley 100 on the trunnion of wheel 64. The ends of 67a are supported on the pulley by compressible members (Lord mounts, springs, etc.) in order to compensate for radius effect on tensile member 67a. Tensile member 67a is secured to the pulley 100 of wheel 64 so that no slippage will occur. Trunnion 64 rotates in the same direction as quadrant 66a.

Similarly, a tensile member 68a (FIG. 11) is attached to quadrant 66a and is threaded around and secured to the pulley 100 on the trunnion of wheel 64b. However, tensile member 68a has its runs crossed over in order to make the trunnion of wheel 64b rotate in a direction opposite from quadrant 66a and from the trunnion of wheel 64. The ends of tensile member 68a are supported on quadrant 66a by compressible members (Lord mounts, springs, etc.) in order to compensate for radius effect on tensile member 68a.

Again, since the trunnion pulleys 100 are all the same size and are equally spaced it can be seen that a projection of the axles of their respective wheels 64 and 64b will coincide at some point along the projection of axles of wheels 63a and 64a if the wheels are turned to any steerable position not parallel to the main frames. The point at which this will occur will move nearer to or further from frames 60 or 60a depending upon the angularity of wheels 64 and 64b.

The wheels 63-63b attached to frame member 60 must be kept in the proper steering relation to those corresponding wheels 64, 64b on frame member 60a. It is therefore necessary to introduce a connecting link between the two. When a vehicle is turning the wheels on the outside of the turn travel in a larger radius than those on the inside; therefore, in Order to reduce tire drag and wear the steering system must compensate for the necessary difference in steering angles. In my design, tensile members 69 and 69a (FIG. 11-12-13) connect quadrants 70 and 70a rotatably, mounted on the undersdes of frame members 60, 60a adjacent quadrants 66, 66a. Thus, these quadrants 70, 70a rotate together and a like amount.

Quadrant 70 has a bellcrank (FIG. 12) formed on its hub as has also quadrant 66, the bellcranks being connected by means of link 71. By properly proportioning the relative lengths and angularities of these bellcranks the quadrant 66 is caused to tum a greater amount in one direction than the other. The required amounts are determined by the dimensions ofthe machine and whatever turning radius is desired.

Similarly, quadrant 70a has a bellcrank (FIG. 1l) fonned on its hub as has also quadrant 66a, the bellcranks being connected by means of link 71a. By properly proportioning the relative lengths and angularities of these bellcranks the quadrant 66a is caused to turn a greater amount in one direction than in the other. The required amounts are determined by the dimensions of the machine and whatever turn radius is desired.

Tensile members 69 and 69a acting through their connecting linkage cause the various steerable wheels 63, 63b, 64, 64b to steer about a common pivot point indicated at 101 in FIG. 12. This point will vary in distance from the frames 60-60a and will change sides when the machine turns in the other direction, but the projections of the various axes of wheels 63, 63b, 64, 64b will always pass through a common point such as 101 on the projection of the axes of wheels 63a-64a during any tum of the wheels.

The force required for steering is supplied by the engine driven pump 72 supplying hydraulic pressure to double-acting hydraulic cylinders 73 and 73a attached to the respective main frames 60, 60a and to the respective bellcrank and quadrant 66 and 66a. The hydraulic pressure and flow is controlled by a valve (not shown) operable adjacent the steering wheel 74 in cab 75. ln this manner full hydraulic power operated steering is accomplished.

THE LIFT ING BEAM ASSEMBLY AND SHIFT CYLINDERS The application of the lift and leveling circuits to the lifting and transporting of containers or other loads is accomplished by a rectangular frame having comers l0, 10a, 10b and 10c.

For simplicities sake, I will refer to it hereafter as lifting beam C. The lifting beam C may have any of several methods for attaching it to a load. It is here shown equipped with a twist lock type of mechanism 102 (FIG. 14) which has become a standard in the containerized freight industry. It is engaged by being inserted into a suitable socket which is integral with the load L, and is then rotated about 90 within the socket. lt will thus support the attached load L until it is disengaged by the operator. In this machine the force required to lock and unlock is supplied by an hydraulic cylinder on the frame 10 (not shown). The operator controls the application of this force by a control valve located in the cab 75. The hydraulic pump 90 (FIGS. 3 and 4) to operate this circuit is located on the engine 66 and serves as a source of power for several other functions.

Lifting beam C is of sandwich design, the lifting frame, per se being disposed on the outside and the guiding beam frame (FIGS. 2 and 7) being disposed on the inside of the beam. The inner or guiding frame 80 of the lifting beam consists of a rectangular frame-work which is carried within the lifting beam frame C, as shown more particularly in FIG. 7, with its ends projecting beyond the lifting frame C at both ends. The end members 80a, 80b of the frame 80 each have a roller 81 (FIGS. 8 and 9) mounted on each end giving a total of four rollers per machine. These rollers 81 move vertically in tracks 82, which are mounted on the arch columns 61 by use of track guides 84 (FIGS. 3 and 4) disposed thereon and near the top of arches 61a. The tracks 82 can be moved vertically in these guides 84. They rest in a socket fitting 88 (FIGS. 3 and 4) on the tops of main frames 60 and 60a. As long as the guide beams 80-80a operate below the tops 61a of the arches 6l-6la, no movement of tracks 82 occurs. When the beam 80-80a is elevated above this point, however, caps 87 (FIG.

) at the tops of the tracks 82 is engaged by cross members 80a and 80h and the tracks 82 are elevated with it. As the beam 80-80a is lowered however the tracks 82 descend with it until their lower ends rest in socket fittings 88 on tops of main lower frame members 60 and 60a. At this point their downward travel is guided by rollers 81 descending in the tracks 82.

The outer framework ofthe lifting beam C contains the four main lifting points l0, 10a, 10b and 10c (FIG. 7) at the corners connected together with suitable members so that the lifting points will remain in the proper relation to suit the load L to be lifted. The end members of lifting beam C are divided into top and bottom chord members and the space in between is left clear for the admission and movement of the guide frame 80, as shown in FIG. 2. All cross members in the lifting beam C follow this pattern. The cross diagonal bracing on this beam C is in the form of tensile X-bracing, as shown in FIG. 2. These bracing members are attached to the top and bottom of the longitudinal members of the lifting beam C.

The guide beam 80 and the lifting beam C are connected near each end by two double-acting hydraulic cylinders, as shown in FIG. 7. Cylinders 85 and 85a are arranged so as to impart relative movement in a lateral direction (crosswise of the machine), and cylinders 86 and 86a are arranged to impart relative movement in a fore-and-aft direction. The cylinders 85 and 85a have independent separate controls in the cab 75. The fore-and-aft cylinders 86 and 86a are interconnected so as to act in concert and are operated by a single control in cab 75. Thus it is possible for the operator to move either end of the lifting beam 10 in a lateral direction or to move the lifting beam fore-and-aft with relation to the rest of the vehicle. He can also cause any combination of the two movements to happen.

The hydraulic force is supplied by the same engine-driven pump v90 used to operate the load and lifting beam locking and unlocking mechanism. The flexible piping used to connect the operator controlled valve to the shift cylinders and twist locks is lead over a cluster of sheaves 89 on lifting beam C and on ram 8b (FIG. 7) as has been standard practice for years in the lift-truck industry.

THE BEAM LIFTING LEVELING CIRCUITS The following mechanism is intended to lift and lower a load L or other object with the attached lifting beam C by use of vertically disposed double-acting hydraulic cylinders 7, 7a, 7b, 7c and related rams 8, 8a, 8b, 8c (FIG. 14) which rams are not directly connected with one another, and each of which rams has a sheave or sprocket 9 attached directly to its exposed upper end. Hydraulic fluid is carried in tank 1 (FIG. 14) and pumped by engine-driven pump 2 to operator controlled valve 3. When valve 3 is in neutral position the fluid circulates through valve 3 and back to tank. Control valve 3 is designed to be used with double-acting cylinders. When pressure is applied to one outlet port the other communicates with the tank 1.

When lever 4 of valve 3 is actuated to the up position fluid from pump 2 flows through valve 3 to a flow divider 5 (FIG. 14) where it is divided into four approximately equal parts, each being routed to a check valve 6, 6a, 6b or 6c at the lower end of its respective cylinder 7, 7a, 7b, 7c thereby extending the related ram 8, 8a, 8b, or 8c which carries its related sheave 9 upwardly and raises its related corner 10, 10a, 10b, 10c of lifting beam C through action of its related tensile member l1, 11a, 11b, llc which is rigidly anchored at the one end 13, 13a, 13b, 13C and attached to lifting beam C at the other. Each tensile member 11, 11a, 11b, llc, which may be a cable or chain, is guided by a sleeve 12 which may either be held rigidly or displaced horizontally in such a manner as to alter the location of the forces acting on the free cylinders 7, 7a, 7b, 7c. The cylinders 7, 7a, 7b, 7c are attached at their bases to the frames 60 or 60a by means of double pivots 107 in such a manner as to allow universal movement of their upper ends in all planes, but preventing rotation of the cylinders. The cylinders 7, 7a, 7b, 7c and rams 8, 8a, 8b, 8c are thus free to equalize or divide the forces acting on lifting beam C and anchors 13, 13a, 13b, 13e through sleeves 12, and thus no bending loads are imposed on the cylinders 7, 7a, 7b, 7c.

When the operator moves control lever 4 (FIG. 14) of valve 3 to Down position, fluid flows through control valve 3 through point 27 to line 28 and to the pilot pistons in valves 6, 6a, 6b, 6c causing same to open. Fluid may then escape through valves 6, 6a, 6b, 6c back to tank l by way of valve 3. Unless pressure is exerted on the said pilot pistons, the pistons in valves 6, 6a, 6b, 6c will close and stop downward movement of rams 8, 8a, 8b, 8c. If downward movement of said rams 8, 8a, 8b, 8c requires more fluid than is supplied by the enginedriven pump 2, the pressure will fall in the system and the pilot pistons in valve 6, 6a, 6b, 6c will allow the valves to close. Thus it is possible for the operator to control speed of both ascent and descent of lifting beam C by controlling the speed of the engine. Pressure applied to the upper sides of the ram pistons at points 28 forces the rams downwardly. If load on any sheave 9 causes it to descend faster than fluid is supplied to point 28, the pressure in line 27 will become too low to hold the related pilot check valve 6 open, and the related ram will stop. Because line 27 communicates with all cylinders at point 28 the pressure therein will be equal and also an equal pressure will be applied to the pilot piston in check valve 6, 6a, 6b, 6c. lf the valves close fluid cannot escape from beneath rams 8, 8a, 8b, 8c and so the rams will stop.

In order to insure that all rams 8, 8a, 8b, 8c will be displaced approximately equal amounts despite variations in load and internal leakage, it is necessary to further refine or trim the system. Means are provided for sensing uneven extension of rams 8, 8a, 8b, 8c, same consisting of a rod member 14, 14a attached to rams 8, 8a, at points 15 and 15a with a ball joint and allowing it to project through a guide sleeve 16 (FIGS. 14-15-16) attached to cylinders 7 with a self-aligning type bearing in such a manner as to allow it to follow changes in angularity of member 14 as the ram 8 moves in or out of cylinder 7 or rotates a fraction of a revolution. A tensile member 17 which may be a chain, cable or tape, is attached to the member 14 at a point 18 and threaded over a sheave or sprocket at point 19 and hence to a similar sheave 20. The member 17 is threaded through a sheave 2l near the base of cylinder 7 c and is attached to the upper end of ram 8c at point 22. It can be seen that as ram 8c extends more cable will be required between points 21 and 22. As ram 8 extends cable will be payed out or grow longer between sheaves 19 and 20. As long as rarns 8 and 8c extend or retract exactly the same amount the tension on member 17 will remain the same. If ram 8c extends faster than ram 8 the tension will increase, but any difference in extension or retraction is immediately sensed by member 17.

Member 17 is threaded through a valve 23a in such a way as to cause fluid to be released from beneath the lower ram 8 or 8c. This is accomplished as follows: If the tension of cable 17 increases above the amount necessary to overcome the spring in the upper end of valve 23a the spool in the valve will be extended allowing fluid from line 26a to pass through valve 23a and to return to tank 1 through line 25. If tension of member 17 decreases enough to allow the spring in valve 23a to retract the spool in the valve, then line 26C will allow fluid to flow through valve 23a and to line 25 and back to tank 1. As one ram overtakes the other `the valve 23a will return to a non-flow or neutral position.

Similarly member 14a is attached to ram 8a at point 15a with a ball joint and projects through guide 16a attached to cylinder 7a with a self-aligning typebearing in such a manner as to allow it to follow changes in angularity of member 14a as ram 8a moves in or out of cylinder 7a or rotates a fraction of a revolution. A tensile member 17a which may be a cable, chain, tape, or the like, is attached to member 14a at point 18a and threaded over one of two aheaves or sprockets 19a (FIGS. 15 and 16) and hence to a similar sheave 29. The cable 17a is also threaded through a sheave 30 near the base of cylinder 7 and is attached to the upper end of ram 8 at point 3l. It can be seen that as ram 8 extends, more cable will be required between points 30 and 31. As ram 8a extends cable will be payed out (grow longer) between sheaves 19 and 29. As long as rams 8 and 8a extend or retract exactly the same amount the tension on member 17a will remain the same. If ram 8 extends faster than ram 8a the tension will increase. Any difference in extension or retraction is immediately sensed by member 17a which is threaded through a valve 23 in such a way as to cause fluid to be released from beneath the longer ram 8 or 8a. This is accomplished in the illustration as follows: If the cable tension increases above the amount necessary to overcome the spring in the upper end of valve 23, the spool of the valve will be extended allowing fluid from line 26 to pass through valve 23 and return to tank 1 through line 25. If ram 8a extends more than ram 8 the tension on member 17a will decrease and allow the spring in valve 23 to retract the spool in valve 23 and allow fluid to flow from cylinder 7a through line 24 through valve 23 and to tank 1 through line 25. As one ram overtakes the other, the valve 23 will return to a non-flow or neutral position.

Similarly, member 14a is attached to ram 8a at point 15a with a ball joint and projects through guide 16a attached to cylinder 7a with a self-aligning type bearing in such a manner as to allow it to follow changes in angularity of member 14a as ram 8a moves in or out of cylinder 7a or rotates a fraction of a revolution. A tensile member 17b (cable, chain, tape, etc.) is attached to member 14a at point 18a and threaded over one of two sheaves or sprockets at point 19a and hence to a similar sheave 32. The member 17b is threaded through a sheave 33 near the base of cylinder 7b and is attached to the upper end of ram 8b at point 34.

It can be seen that as ram 8b extends more cable will be required between points 34 and 33. As ram 8a extends cable will be paid out (grow longer) between points 19a and 32. As long as ram 8a and 8b extends or retracts exactly the same amount the tension on member 17b will remain the same. If ram 8b extends faster than 8a the tension will increase. Any difference in extension or retraction is immediately sensed by member 17b which is threaded through a valve 23b or switch in such a way as to cause fluid to be released from beneath the longer ram 8a or 8b. This is accomplished in the illustration as follows: If cable tension increases above the amount necessary to overcome the spring in the upper end of valve 23b, the spool will be extended allowing fluid from line 24a to pass from 7b through valve 23b and return to tank through line 25. If ram 8a extends more than ram 8b` the tension on member 17b will decrease and allow the spring in valve 23b to retract the spool in the valve, and allow fluid to flow from 7a through 24b through 23b and to tank through line 25. As one ram overtakes the other the valve 23b will return to a no-flow or neutral position.

The practical effect of all this arrangement is to stop or slow the extension of the furthest extended ram until the other overtakes it. This will come about because approximately the same volume of fluid is delivered by the flow divider to each cylinder 7, 7a, 7b, 7c and its ram. Since the longest extended ram has some of its fluid returned to the tank 1 by action of valve 23, 23a, or 23b, it will slow or halt until such time as valve 23, 23a, or 23b closes. The volume of fluid delivered by the flow divider 5 will determine the rate of extension. When the rams are descending the action of valve 23, 23a, or 23b is to allow an additional route for fluid to escape from beneath ram 8, 8a, 8b, or 8c, thus hastening its rate of descent and allowing it to overtake the others.

Referring to FIG. 17, hydraulic fluid is drawn from reservoir 41 by pump 42, and flows to control valve 43 through line 44 and back to reservoir 41Athrough line 45. Control valve 43 is designed to be used with double-acting hydraulic cylinders. When pressure is applied to one outlet port the other communicates with the reservoir. If the operator moves control lever 46 to the left the fluid is diverted through valve 43 to line 47 to cylinders 48 and 48a. Fluid enters cylinder 48 at point 49 and exerts pressure on ram causing it to extend, forcing guide 12 laterally toward cylinder 7, thus displacing tensile member l1, causing it to exert pressure on sheave 9 and displace it toward the center line of the machine, as shown in FIG. 17. This in turn displaces beam 10 or 10a in a like manner.

Line 47 also carries fluid to point 50a on cylinder 48a causing it to retract its ram and exert pressure on guide 12a in a direction away from the center line of the machine. This force acting on sheave 9a of ram 8a through tensile member 11a causes said sheave 9a to be displaced outwardly from the center line of the machine and causes the lifting beam C to move in a like manner.

Line 47 also carries fluid to point 50a on cylinder 48a causing it to retract its ram and exert pressure on guide 12a in a direction away from the center line of the machine. This force acting on sheave 9 of ram 8a through tensile member 11a causes said sheave 9 to be displaced outwardly from the center line of the machine and causes the lifting beam C to move in a like manner.

lf the operator moves control lever 46 towards the right (FIG. 17) the process will be reversed. In this instance, fluid will flow through valve 43 and line 51 to cylinder 48 at point 50 causing it to retract the ram and guide 12 with it. This will exert a force on tensile member 11 in a direction away from the center line of the machine. Member 1l will cause sheave 9 to move away from the center line and cause lifting beam C to move in a like direction. Fluid will enter cylinder 48a at point 49a causing it to exert pressure on its related sheave 9a in a direction toward the center of the machine. Said sheave 9a acting through member 11a exerts force on lifting beam C in a like direction. Cylinder 48 and 48a acting in concert make it possible for the operator to control the position of the lifting beam C in relation to the center line of the machine.

THE VEHICLE WHEEL SUSPENSION As above described, the vehicle frame is supported by six hydraulic assemblies which are alike in all basic details. Two of them on each side of the vehicle are connected together to insure equal traction and braking. As shown in FIG. 18, trunnion 163 is supported inside housing 164 by bearings 165. The lower end of housing 164 is closed by a packing 166 to prevent escape of oil or gas. To prevent the trunnion 163 from over extension piston rod 167 is attached to housing 164 at point 168. Cylinder 169 is attached to trunnion 163 at point 170. The piston rod 167 has a piston head 171 formed on its lower end which is disposed within cylinder 169. The piston head 171 is larger than the opening in bulkhead 172 for the rod 167. When the piston 171 has reached bulkhead 172 no further extension is possible and thus the trunnion 163 is prevented from extending below the desired length.

With the trunnion fully retracted, as in FIG. 19, the housing 164 is filled with oil through filler plug 173. Filler 173 has an air check valve similar to that used on pneumatic tires incorporated into it. Compressed air or gas is introduced into housing 164 through valve 173 causing trunnion 163 to extend (FIG. 18) until the frame 60 or 60A (FIG. 21) is supported at the desired height. The compressed air or gas within housing 164 thus serves as a spring to support the vehicle. The air or gas also serves as a thrust bearing enabling the trunnion 163 to rotate as well as to move vertically.

The interior of the housing shown in FIG. 19 is filled with oil and hence cylinder 169 and piston 171 are submerged in oil. The piston 171 and cylinder 169 thus serve to restrain the actions of trunnion 163. The degree of restraint is controlled by the amount of clearance between piston 171 and cylinder 169 and between piston rod 167 and bulkhead 172. A hole 174 (FIG. 20) is drilled in the cylinder 169 to allow oil to escape during part of the travel thus reducing the Dash Pot effect near the mid-point of travel.

A tube 175 connects those housings 164 attached to wheels 63a and 63h and also a similar tube 175a connects the housings attached to wheels 64a and 64b. This allows air or gas to travel from one of a respective pair to the other. In this manner the load supported by each will be substantially the same as long as the effective travel of the trunnions 163 is not exceeded` This is to insure that the drive wheels 63 and 64 will have enough weight for traction when the center wheels 63a and 64a runover a high spot such as the crown in a street or similar situation. FIG. shows the trunnion 163 fully extended and being retained by the action of rod 167 and cylinder 169. FIG. 21 shows the tube 175 in relation to the housings 164 attached to frame 60. A like situation exists on frame 60a.

Iclaim:

l. A straddle carrier comprising a pair of longitudinally extending parallel spaced elongated frame members adapted to carry a load; said parallel frame members being connected adjacent their ends by a pair of arches, the whole forming a rectangular, unobstructed, open topped bay extending vertically from ground level to infinity; diagonally disposed brace members connecting the tops of the arches to substantially the mid-points of said frame members; ground wheels flexibly mounted on the frame members; means for steering said wheels without direct across-the-frame linkage of any wheel with the corresponding wheel on the frame opposite; a rectangular load lifting beam disposed within the open bay between the frame members and the arches, said beam being shorter than the distance between the arches; means engaging the four corners of the lifting beam for raising and lowering same, extension of said means not being limited by the height of the arches whereby the lifting beam can be raised above the arches; said means being attached to, and supported by, the parallel frame members; means at the four corners of the lifting beam for securing same to the load; means on the lifting beam and arches for guiding the lifting beam during its ascent and descent; and means for controlling the lifting beam raising and lowering means whereby the four corners of said beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on said respective corners, in order to maintain the beam always parallel with said frame members.

2. In a carrier as set forth in claim l, three vertically movable equally spaced ground wheels being mounted in trunnions disposed in each frame member, the end wheels being steerable and the center wheels for each frame member being nonsteerable; and said steering means comprising means for simultaneously actuating the end wheels on each frame member regardless of the radius of curvature of any steering course, the end wheels on any given frame member turning through the same but opposite angularity, whereby the projection of the axes of rotation of the end wheels, both those of the innermost and outermost frame members when the wheels are turned from a straightline position, will always intersect the axis of rotation of the center wheels at a common point for all radii of curvature in steering.

3. In a carrier as set forth in claim 2, drive motors mounted on the hubs of one end wheel of each frame member; a variable displacement pump mounted on one frame member, flexible piping connecting the pump with said motors respectively; a cab mounted on the outer face of the top of one arch member; and means in said cab for controlling said pump.

4. In a carrier as set forth in claim 2, said means for simultaneously actuating the end wheels comprising pulleys mounted on the trunnions of the end wheels quadrants journalled on the respective frames intermediate the end wheels; cables having their ends secured to the respective quadrants and threaded around the pulleys for the trunnions of one end wheel of the respective frame; other cables having their ends secured to the respective quadrants and their runs crossed over and threaded around the pulleys for the trunnion of the other end wheel of the respective frame; other quadrants journaled in the respective frames adjacent the first quadrants further cables threaded around the other quadrants on the two frames to cause same to rotate together like amounts; said first quadrants and other quadrants having bellcranks; links connecting the said bellcranks; the relative lengths and angularities of the bellcranks being proportioned to cause the wheels to turn a greater amount in one direction than in the other; and means for rotating the first quadrants,

5. In a carrier as set forth in claim 4, said rotating means comprising double acting hydraulic cylinder attached to the respective frame members and having pistons attached to the respective first quadrants; a cab mounted on the outer face of the top of one arch member; and valve means in said cab for controlling said cylinders.

6. ln a carrier as set forth in claim 2, housings in the frame members receiving the trunnions of each ground wheel; oil packings disposed between the lower ends of the housings and said trunnions; said trunnions being hollow and having open upper ends within the housings; means for preventing over-ex tension of the trunnions; said housings having closed upper ends and being fillable with oil through filler plugs disposed in said closed upper ends when the trunnions are fully retracted; said filler plugs having air check valves therein whereby com pressed air may be introduced into the housings causing the trunnions to extend downwardly to support the frame members at any desired height; said compressed air also serving as springs to support the frame members and serving as thrust bearings permitting rotation of and vertical movement of the trunnions of the end wheels in the housings.

7. ln a carrier as set forth in claim 6, said preventing means comprising piston rods having their upper ends secured to the closed upper ends of the housings and having enlarged pistons at their lower ends, cylinders tixed within the hollow upper portions of the trunnions receiving said pistons; bulkhead rings at the upper ends of the cylinders above the pistons limiting the extending movement of the trunnions; and a vent hole in each cylinder wall permitting oil to escape during part of its travel thereby reducing dash pot effect near the mid-point of travel of the cylinder.

8. ln a carrier as set forth in claim 6, a pipe interconnecting the housings for the center wheel and the non-driving end wheel of each frame member respectively allowing air to travel from one housing to the other, whereby the load supported by each interconnected housing will be substantially the same as long as the effective travel of the trunnions is not exceeded, thereby insuring that the driving end wheels will have enough weight thereon for traction when the center wheels run over a high spot in the road surface.

9. In a carrier as set forth in claim 1, said load lifting beam comprising an outer rectangular frame; an inner rectangular frame shiftable laterally and longitudinally with respect to the outer frame; the ends of the inner frame extending beyond the ends of the outer frame; double-acting hydraulic cylinders having pistons connecting the ends of the inner frame and outer frame adapted to impart relative movement of the frames in a fore-and-aft direction; other double-acting hydraulic cylinders connecting the ends of the inner and outer frames adapted to impart relative movement of the frames in a lateral direction; a cab mounted on the outer face of the top of one arch member; and means in said cab for controlling said cylinders.

10. In a carrier as set forth in claim 9, said means for guiding said lifting beam comprising rollers at the four corners of the inner frame, telescoping tracks on the vertical legs of the arch members receiving said rollers, said tracks being movable vertically in guides disposed along the arches, said tracks being of such height that as long as the lifting beam is operating below the tops of the arches no movement of the tracks will occur, but when the lifting beam is elevated above the arches the rollers will engage plates at the tops of the tracks and will elevate the tracks in their guides with the lifting beam; and sockets on the carrier frame members below the tracks normally receiving the lower ends of the tracks.

11. In a carrier as set forth in claim l, said lifting beam raising and lowering means comprising non-rotatable upwardly disposed double-acting hydraulic cylinders having their lower ends connected by universal joints to the frame members adjacent the comers of the lifting beam; upwardly movable rams in said cylinders respectively; pulleys mounted on the upper ends of the rams respectively on axes parallel with the longitudinal axis of the frame members; cables connected with the four comers of the lifting beam respectively and extending over said pulleys with their outer ends adjustably secured to the frame members adjacent the respective universal joints, whereby as the rams are simultaneously activated the corners of the lifting beam will be simultaneously vertically moved; and guide sleeves through which the cables run respectively for normally maintaining the cylinders and rams in substantially upright positions without direct attachment of the rams to one another.

12. ln a carrier as set forth in claim 11, said controlling means comprising a fluid circuit including a fluid tank, a pump, an operator-controlled valve, and a flow divider, said divider dividing the fluid delivered thereto into four substantially equal parts, each of which parts is delivered to a related check valve at the lower end of its related hydraulic cylinder to move its related ram; said check valves having pilot pistons therein adapted to open when fluid is passing thereto, said fluid escaping through said check valves and passing back to the tank, and siad pistons closing when no fluid pressure is exerted thereon, thereby stopping movement of the related ram; said check valves discharging into the upper and lower ends of the hydraulic cylinders whereby the operator may control the speed of ascent and descent of the lifting beam by controlling the speed of the pump.

13. ln a carrier as set forth in claim 12, means for sensing uneven extensions of the rams due to variations in load on the four corners of the lifting beam comprising rods having their upper ends secured to the rams respectively, the lower ends of the rods projecting through guide sleeves attached to their related cylinders with self-aligning type bearings to allow same to follow changes in angularity of the rods as the rams move in and out of their related cylinders; tensile cables having one end secured to their related rods and passing under sheaves at the bases of the related cylinder and at the base of an adjacent cylinder; the other ends of the tensile cables being attached to the upper end of the ram of said adjacent cylinder; said tensile members having loops intermediate the sheaves; valves in the fluid circuit having spring-operated spools over which the loop is threaded, whereby if tension on the tensile cable increases above the amount necessary to overcome the spring fluid may pass through said valves and return to the fluid tank, but if the tension decreases an amount sufficient to allow the springs to retract the spools then the fluid may pass through the valves and through another line back to the tank, and whereby as one ram overtakes the other the valves will return to non-flow positions.

14. In a carrier as set forth in claim 1l, said guide sleeves being mounted on the piston rods of double-acting hydraulic cylinders mounted on the frame members respective; a fluid circuit including a reservoir, a pump, and a control valve having ports connected to the ends of said cylinders whereby when the valve is in one position fluid will be admitted into opposite ends of said cylinders to shift the cables simultaneously in one direction, and when the valve is in the other position fluid will be admitted into the opposite ends of said cylinders to shift the cables simultaneously in the other direction, whereby the operator may control the position of the lifting beam in relation to the center line of the vehicle.

l5. In a wheeled vehicle, a load lifting beam comprising an outer rectangular frame; an inner rectangular frame shiftable laterally and longitudinally with respect to the outer frame; the ends of the inner frame extending beyond the ends of the outer frame; means for guiding said lifting beam; means for raising and lowering the lifting beam; double-acting hydraulic cylinders having pistons connecting the ends of the inner frame and outer frame adapted to impart relative movement of the frames in a fore-and-aft direction; other double-acting hydraulic cylinders connecting the ends of the inner and outer frames adapted to impart relative movement of the frames in a lateral direction; and means for controlling said cylinders.

16. In a vehicle as set forth in claim 15, said means for guiding said lifting beam comprising rollers at the four comers of the inner frame; telescoping tracks on the vehicle frame receiver said rollers, said tracks being movable vertically in guides, said tracks being of such height that as long as the lifting beam is operating below the normal tops of the tracks no movement of the tracks will occur, but when the lifting beam is elevated above the tops of the tracks the rollers will engage plates at the tops of the tracks and will elevate the tracks in their guides with the lifting beam; and sockets on the vehicle frame below the tracks normally receiving the lower ends of the tracks.

17. ln a vehicle as set forth in claim 15, said lifting beam raising and lowering means comprising non-rotatable upwardly disposed double-acting hydraulic cylinders having their lower ends connected by universal joints to the frame adjacent the corners of the lifting beam; upwardly movable rams in said cylinders respectively; pulleys mounted on the upper ends of the rams respectively on axes parallel with the longitudinal axis of the frame; cables connected with the four corners of the lifting beam respectively and extending over said pulleys with their outer ends adjustably secured to the frame members adjacent the respective universal joints whereby as the rams are simultaneously activated the corners of the lifting beam will be simultaneously upwardly moved; and guide sleeves through which the cables run respectively for normally maintaining the cylinders and rams in substantially upright positions without direct attachment of the rams to one another.

18. ln a vehicle as set forth in claim 15, said controlling means comprising a fluid circuit including a fluid tank, a pump, an operator-controlled valve, and a flow divider, said divider dividing the fluid delivered thereto into four substantially equal parts, each of which parts is delivered to a related check valve at the lower end of its related hydraulic cylinder to move its related ram; said check valves having pilot pistons therein adapted to open when fluid is passing thereto, said fluid escaping through said check valves and passing back to the tank, and said pistons closing when no fluid pressure is exerted thereon, thereby stopping movement of the related ram; said check valves discharging into the upper and lower ends of the hydraulic cylinders whereby the operator may control the speed of ascent and descent of the lifting beam by controlling the speed of the pump.

19. In a vehicle as set forth in claim 18, means for sensing eneven extensions of the rams due to variations in load on the four comers of the lifting beam comprising rods having their upper ends secured to the rams respectively, the lower ends of the rods projecting through guide sleeves attached to their related cylinders with self-aligning type bearings to allow same to follow chan ges in angularity of the rods as the rams move in and out of their related cylinders; tensile cables having one end secured to their related rods and passing under sheaves at the bases of the related cylinder and at the base of an adjacent cylinder; the other ends of the tensile cables being attached to the upper end of the ram of said adjacent cylinder; said tensile members having loops intermediate the sheaves; valves in the fluid circuit having spring operated spools over which the loop is threaded, whereby if tension on the tensile cable increases above the amount necessary to overcome the spring fluid may pass through said valves and return to the fluid tank, but if the tension decreases an amount sufficient to allow the springs to retract the spools then the fluid may pass through the valves and through another line back to the tank, and whereby as one rarn overtakes the other the valves will return to non-flow positions.

20. In a vehicle as set forth in claim 17, said guide sleeves being mounted on the piston rods of double-acting hydraulic cylinders mounted on the frame members respective; a fluid circuit including a reservoir, a pump, and a control valve -having ports connected to the ends of said cylinders whereby 

1. A straddle carrier comprising a pair of longitudinally extending parallel spaced elongated frame members adapted to carry a load; said parallel frame members being connected adjacent their ends by a pair of arches, the whole forming a rectangular, unobstructed, open topped bay extending vertically from ground level to infinity; diagonally disposed brace members connecting the tops of the arches to substantially the mid-points of said frame members; ground wheels flexibly mounted on the frame members; means for steering said wheels without direct across-the-frame linkage of any wheel with the corresponding wheel on the frame opposite; a rectangular load lifting beam disposed within the open bay between the frame members and the arches, said beam being shorter than the distance between the arches; means engaging the four corners of the lifting beam for raising and lowering same, extension of said means not being limited by the height of the arches whereby the lifting beam can be raised above the arches; said means being attached to, and supported by, the parallel frame members; means at the four corners of the lifting beam for securing same to the load; means on the lifting beam and arches for guiding the lifting beam during its ascent and descent; and means for controlling the lifting beam raising and lowering means whereby the four corners of said beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on said respective corners, in order to maintain the beam always parallel with said frame members.
 2. In a carrier as set forth in claim 1, tHree vertically movable equally spaced ground wheels being mounted in trunnions disposed in each frame member, the end wheels being steerable and the center wheels for each frame member being non-steerable; and said steering means comprising means for simultaneously actuating the end wheels on each frame member regardless of the radius of curvature of any steering course, the end wheels on any given frame member turning through the same but opposite angularity, whereby the projection of the axes of rotation of the end wheels, both those of the innermost and outermost frame members when the wheels are turned from a straightline position, will always intersect the axis of rotation of the center wheels at a common point for all radii of curvature in steering.
 3. In a carrier as set forth in claim 2, drive motors mounted on the hubs of one end wheel of each frame member; a variable displacement pump mounted on one frame member, flexible piping connecting the pump with said motors respectively; a cab mounted on the outer face of the top of one arch member; and means in said cab for controlling said pump.
 4. In a carrier as set forth in claim 2, said means for simultaneously actuating the end wheels comprising pulleys mounted on the trunnions of the end wheels'' quadrants journalled on the respective frames intermediate the end wheels; cables having their ends secured to the respective quadrants and threaded around the pulleys for the trunnions of one end wheel of the respective frame; other cables having their ends secured to the respective quadrants and their runs crossed over and threaded around the pulleys for the trunnion of the other end wheel of the respective frame; other quadrants journaled in the respective frames adjacent the first quadrants'' further cables threaded around the other quadrants on the two frames to cause same to rotate together like amounts; said first quadrants and other quadrants having bellcranks; links connecting the said bellcranks; the relative lengths and angularities of the bellcranks being proportioned to cause the wheels to turn a greater amount in one direction than in the other; and means for rotating the first quadrants.
 5. In a carrier as set forth in claim 4, said rotating means comprising double acting hydraulic cylinder attached to the respective frame members and having pistons attached to the respective first quadrants; a cab mounted on the outer face of the top of one arch member; and valve means in said cab for controlling said cylinders.
 6. In a carrier as set forth in claim 2, housings in the frame members receiving the trunnions of each ground wheel; oil packings disposed between the lower ends of the housings and said trunnions; said trunnions being hollow and having open upper ends within the housings; means for preventing over-extension of the trunnions; said housings having closed upper ends and being fillable with oil through filler plugs disposed in said closed upper ends when the trunnions are fully retracted; said filler plugs having air check valves therein whereby compressed air may be introduced into the housings causing the trunnions to extend downwardly to support the frame members at any desired height; said compressed air also serving as springs to support the frame members and serving as thrust bearings permitting rotation of and vertical movement of the trunnions of the end wheels in the housings.
 7. In a carrier as set forth in claim 6, said preventing means comprising piston rods having their upper ends secured to the closed upper ends of the housings and having enlarged pistons at their lower ends, cylinders fixed within the hollow upper portions of the trunnions receiving said pistons; bulkhead rings at the upper ends of the cylinders above the pistons limiting the extending movement of the trunnions; and a vent hole in each cylinder wall permitting oil to escape during part of its travel thereby reducing ''''dash pot'''' effect near the mid-point of travel of the cylinder.
 8. In a caRrier as set forth in claim 6, a pipe interconnecting the housings for the center wheel and the non-driving end wheel of each frame member respectively allowing air to travel from one housing to the other, whereby the load supported by each interconnected housing will be substantially the same as long as the effective travel of the trunnions is not exceeded, thereby insuring that the driving end wheels will have enough weight thereon for traction when the center wheels run over a high spot in the road surface.
 9. In a carrier as set forth in claim 1, said load lifting beam comprising an outer rectangular frame; an inner rectangular frame shiftable laterally and longitudinally with respect to the outer frame; the ends of the inner frame extending beyond the ends of the outer frame; double-acting hydraulic cylinders having pistons connecting the ends of the inner frame and outer frame adapted to impart relative movement of the frames in a fore-and-aft direction; other double-acting hydraulic cylinders connecting the ends of the inner and outer frames adapted to impart relative movement of the frames in a lateral direction; a cab mounted on the outer face of the top of one arch member; and means in said cab for controlling said cylinders.
 10. In a carrier as set forth in claim 9, said means for guiding said lifting beam comprising rollers at the four corners of the inner frame, telescoping tracks on the vertical legs of the arch members receiving said rollers, said tracks being movable vertically in guides disposed along the arches, said tracks being of such height that as long as the lifting beam is operating below the tops of the arches no movement of the tracks will occur, but when the lifting beam is elevated above the arches the rollers will engage plates at the tops of the tracks and will elevate the tracks in their guides with the lifting beam; and sockets on the carrier frame members below the tracks normally receiving the lower ends of the tracks.
 11. In a carrier as set forth in claim 1, said lifting beam raising and lowering means comprising non-rotatable upwardly disposed double-acting hydraulic cylinders having their lower ends connected by universal joints to the frame members adjacent the corners of the lifting beam; upwardly movable rams in said cylinders respectively; pulleys mounted on the upper ends of the rams respectively on axes parallel with the longitudinal axis of the frame members; cables connected with the four corners of the lifting beam respectively and extending over said pulleys with their outer ends adjustably secured to the frame members adjacent the respective universal joints, whereby as the rams are simultaneously activated the corners of the lifting beam will be simultaneously vertically moved; and guide sleeves through which the cables run respectively for normally maintaining the cylinders and rams in substantially upright positions without direct attachment of the rams to one another.
 12. In a carrier as set forth in claim 11, said controlling means comprising a fluid circuit including a fluid tank, a pump, an operator-controlled valve, and a flow divider, said divider dividing the fluid delivered thereto into four substantially equal parts, each of which parts is delivered to a related check valve at the lower end of its related hydraulic cylinder to move its related ram; said check valves having pilot pistons therein adapted to open when fluid is passing thereto, said fluid escaping through said check valves and passing back to the tank, and siad pistons closing when no fluid pressure is exerted thereon, thereby stopping movement of the related ram; said check valves discharging into the upper and lower ends of the hydraulic cylinders whereby the operator may control the speed of ascent and descent of the lifting beam by controlling the speed of the pump.
 13. In a carrier as set forth in claim 12, means for sensing uneven extensions of the rams due to variations in load on the four corners of the lifting beam comprising rods havIng their upper ends secured to the rams respectively, the lower ends of the rods projecting through guide sleeves attached to their related cylinders with self-aligning type bearings to allow same to follow changes in angularity of the rods as the rams move in and out of their related cylinders; tensile cables having one end secured to their related rods and passing under sheaves at the bases of the related cylinder and at the base of an adjacent cylinder; the other ends of the tensile cables being attached to the upper end of the ram of said adjacent cylinder; said tensile members having loops intermediate the sheaves; valves in the fluid circuit having spring-operated spools over which the loop is threaded, whereby if tension on the tensile cable increases above the amount necessary to overcome the spring fluid may pass through said valves and return to the fluid tank, but if the tension decreases an amount sufficient to allow the springs to retract the spools then the fluid may pass through the valves and through another line back to the tank, and whereby as one ram overtakes the other the valves will return to non-flow positions.
 14. In a carrier as set forth in claim 11, said guide sleeves being mounted on the piston rods of double-acting hydraulic cylinders mounted on the frame members respective; a fluid circuit including a reservoir, a pump, and a control valve having ports connected to the ends of said cylinders whereby when the valve is in one position fluid will be admitted into opposite ends of said cylinders to shift the cables simultaneously in one direction, and when the valve is in the other position fluid will be admitted into the opposite ends of said cylinders to shift the cables simultaneously in the other direction, whereby the operator may control the position of the lifting beam in relation to the center line of the vehicle.
 15. In a wheeled vehicle, a load lifting beam comprising an outer rectangular frame; an inner rectangular frame shiftable laterally and longitudinally with respect to the outer frame; the ends of the inner frame extending beyond the ends of the outer frame; means for guiding said lifting beam; means for raising and lowering the lifting beam; double-acting hydraulic cylinders having pistons connecting the ends of the inner frame and outer frame adapted to impart relative movement of the frames in a fore-and-aft direction; other double-acting hydraulic cylinders connecting the ends of the inner and outer frames adapted to impart relative movement of the frames in a lateral direction; and means for controlling said cylinders.
 16. In a vehicle as set forth in claim 15, said means for guiding said lifting beam comprising rollers at the four corners of the inner frame; telescoping tracks on the vehicle frame receiver said rollers, said tracks being movable vertically in guides, said tracks being of such height that as long as the lifting beam is operating below the normal tops of the tracks no movement of the tracks will occur, but when the lifting beam is elevated above the tops of the tracks the rollers will engage plates at the tops of the tracks and will elevate the tracks in their guides with the lifting beam; and sockets on the vehicle frame below the tracks normally receiving the lower ends of the tracks.
 17. In a vehicle as set forth in claim 15, said lifting beam raising and lowering means comprising non-rotatable upwardly disposed double-acting hydraulic cylinders having their lower ends connected by universal joints to the frame adjacent the corners of the lifting beam; upwardly movable rams in said cylinders respectively; pulleys mounted on the upper ends of the rams respectively on axes parallel with the longitudinal axis of the frame; cables connected with the four corners of the lifting beam respectively and extending over said pulleys with their outer ends adjustably secured to the frame members adjacent the respective universal joints whereby as the rams are simultaneously activated the corners of the liftinG beam will be simultaneously upwardly moved; and guide sleeves through which the cables run respectively for normally maintaining the cylinders and rams in substantially upright positions without direct attachment of the rams to one another.
 18. In a vehicle as set forth in claim 15, said controlling means comprising a fluid circuit including a fluid tank, a pump, an operator-controlled valve, and a flow divider, said divider dividing the fluid delivered thereto into four substantially equal parts, each of which parts is delivered to a related check valve at the lower end of its related hydraulic cylinder to move its related ram; said check valves having pilot pistons therein adapted to open when fluid is passing thereto, said fluid escaping through said check valves and passing back to the tank, and said pistons closing when no fluid pressure is exerted thereon, thereby stopping movement of the related ram; said check valves discharging into the upper and lower ends of the hydraulic cylinders whereby the operator may control the speed of ascent and descent of the lifting beam by controlling the speed of the pump.
 19. In a vehicle as set forth in claim 18, means for sensing eneven extensions of the rams due to variations in load on the four corners of the lifting beam comprising rods having their upper ends secured to the rams respectively, the lower ends of the rods projecting through guide sleeves attached to their related cylinders with self-aligning type bearings to allow same to follow changes in angularity of the rods as the rams move in and out of their related cylinders; tensile cables having one end secured to their related rods and passing under sheaves at the bases of the related cylinder and at the base of an adjacent cylinder; the other ends of the tensile cables being attached to the upper end of the ram of said adjacent cylinder; said tensile members having loops intermediate the sheaves; valves in the fluid circuit having spring operated spools over which the loop is threaded, whereby if tension on the tensile cable increases above the amount necessary to overcome the spring fluid may pass through said valves and return to the fluid tank, but if the tension decreases an amount sufficient to allow the springs to retract the spools then the fluid may pass through the valves and through another line back to the tank, and whereby as one ram overtakes the other the valves will return to non-flow positions.
 20. In a vehicle as set forth in claim 17, said guide sleeves being mounted on the piston rods of double-acting hydraulic cylinders mounted on the frame members respective; a fluid circuit including a reservoir, a pump, and a control valve having ports connected to the ends of said cylinders whereby when the valve is in one position fluid will be admitted into opposite ends of said cylinders to shift the cables simultaneously in one direction, and when the valve is in the other position fluid will be admitted into the opposite ends of said cylinders to shift the cables simultaneously in the other direction, whereby the operator may control the position of the lifting beam in relation to the center line of the vehicle. 